It is known in the art to prepare a variety of alumina-silicate products utilizing a variety of silica and alumina sources.
U.S. Pat. No. 4,247,420 to Dumoulin et al relates to the preparation of hydrocarbon conversion catalysts by mixing a sodium silicate solution with an aluminum sulfate solution at a pH 9.0-9.6. To this co-gel a sodium aluminate solution is added to a pH 11.8-12.2. Alum is added again to a pH 3.5-4.0. A zeolite Y and/or a sodium silicate solution are then added and the precipitate slurry is filtered and washed to remove soluble sodium sulfate and dried. This process and product obtained thereof are different from those of the present invention in that a sodium silicate solution is utilized and that a co-gel is formed when the aluminum sulfate solution is added rather than a solution or sol when a source of silica or silicate is mixed with the alum. The proportions of the different components of this product are in addition different from those of the product of the invention.
U.S. Pat. No. 3,424,602 to Nauroth mixes a soluble sodium silicate with an aluminum sulfate solution to form sodium alumino silicate precipitates. The final product is also different from the alumina-silica-sulfates of this invention in that the precipitate is a product substantially lacking in sulfate content, with sulfate only present as sodium sulfate by-product.
U.S. Pat. No. 2,768,145 to Tongue first produces a conventional silica gel by reacting an acid and a sodium silicate solution (no aluminum is present at this point). The precipitation-gelation of particles in the slurry is completed by adding sulfuric acid. The resulting particles of silica hydrogel are then impregnated with aluminum by adding a solution of aluminum sulfate to the acidified slurry. The aluminum is precipitated as a substantially insoluble hydrated alumina by the further addition of aqueous ammonia. The resulting product is spray-dried to form spherical particles which do not contain sulfate.
U.S. Pat. Nos. 3,582,379 and 3,832,327 to Hackbarth relate to the production of alkali metal alumino silicates prepared by reacting dilute aqueous solutions of an alkali metal silicate and a water soluble aluminum salt such as aluminum sulfate. No sols or gels are formed in this process.
U.S. Pat. Nos. 1,515,007 and 1,736,281 to Behrman disclose methods for the preparation of gel materials by reacting a solution of sodium silicate and a solution of aluminum sulfate. The term "gel" is used in the Behrman patent to represent precipitated sodium alumino silicates similar to the aforementioned Hackbarth patents. After the precipitate is obtained, it is dried and then washed to remove any soluble sodium sulfate remaining therein.
U.S. Pat. No. 3,041,269 to Anderson relates to a process for producing a hydrocarbon cracking catalyst containing silica, alumina and barium sulfate. The silica and alumina are present as a silica-alumina sol having a pH 8.0-9.0 and the barium sulfate is dispersed therewithin. Once obtained the mixture is base-exchanged and washed to a point where it is salt free, i.e., sulfate free. More specifically, the aluminum sulfate contains added sulfuric acid and the silica is in the form of a sodium silicate solution. These two solutions are reacted in the presence of added insoluble barium sulfate. The reactants are mixed in a spray head and spheres are formed by adding this gel slurry into an oil medium.
U.S. Pat. No. 2,551,014 to Kimberlin provides a process comprising the addition of aluminum sulfate to a silica hydrosol, and the further addition of an insoluble magnesium oxide slurry. The slurry is added into an oil to form the microspheres which are then washed salt free, i.e., sulfate-free.
U.S. Pat. No. 2,302,297 to Connolly relates to a process comprising mixing soluble sodium silicate and aluminum sulfate solution to form a silica-alumina hydrogel containing soluble sodium sulfate. The silica:alumina molar ratio of the product is 2.0:15.0, which is substantially higher than the silica:alumina ratio in the product of the present invention.
U.S. Pat. No. 3,533,738 to Rundell discloses a process which comprises producing a solution of soluble sodium silicate having an excess of sodium hydroxide, and then reacting it with a solution of either a combination of sodium aluminate and aluminum nitrate in one example or with aluminum nitrate only in another example. A co-gel formed is then spray-dried, calcined, washed and ammonium sulfate-exchanged to remove Na.sub.2 O. The product is exchanged after drying and before calcining. The claimed level of Na.sub.2 O in the Rundell patent is about 0.20 wt.% which is substantially below the minimum 1.0 wt.% of the present alumina-silica-sulfate. The product does not appear to contain bound sulfate. Although spray dried, it is not specifically stated in this patent whether a spherical product is obtained or desired. The emphasis of the Rundell patent is the production of synthetic mullite by calcining.
U.S. Pat. No. 3,993,499 to Jacobson discloses a process comprising reacting dry sodium silicate and aluminum sulfate in the presence of additional sodium sulfate and/or sodium chloride to form a gel which is then dried, leached, fired to remove sulfate and form mullite preferably in the form of fibrils. The products obtained by Jacobson contain excess alkali metal sulfate or chloride salt added to promote mullite fibril growth which is absent in the present invention. Jacobson also mixes the reactants, including the excess salts, to form a hard gel which is then dried in a brick, calcined and then leached to remove sulfates. In order to avoid the formation of mullite in the present invention the reaction mixture is maintained as a sol to facilitate its spray drying to form microspheres.
The present invention provides novel alumina-silica-sulfates, microspheres thereof, compositions thereof which are useful as desiccants, carriers, and catalyst supports and a method of preparing the products.
None of the prior art patents teach the novel alumina-silica-sulfate compositions of the invention or the method of their synthesis as described herein. The products of the present invention are unique and useful products.